This invention relates generally to automatic guidance control systems for controlling the direction of travel of a moving vehicle to follow a prescribed path. More particularly, the present invention relates to an automatic guidance control system for guiding an agricultural tractor to follow a previously plowed furrow or guiding means in a field under cultivation.
The need to produce the maximum amount of agricultural products from a given amount of acreage is becoming more and more important as the result of an ever increasing demand for these products and the increasing costs to produce them. To meet this growing demand, it is necessary that the land under cultivation be plowed and planted so that there is little wasted land. Each plowed furrow should be parallel with all other furrows and spaced at very accurate seperation distances.
Prior-art tractor guidance systems have been constructed to guide the path of the tractor to follow a previously plowed furrow. However, these prior-art guidance systems are, for the most part, complicated mechanical-hydraulic contrivances that lack the sensitivity necessary to optimally control the direction of travel of the tractor to follow a previously plowed furrow. Additionally, these types of prior-art devices are only effective when used on tractors which have closed center hydraulic systems. Not all tractors come so equipped. Another problem not solved by these prior-art devices occurs from external forces which act on the tractor and the implements being pulled to force the tractor to deviate in its direction of travel, without a change in the tractor's steering direction. These external forces result from such things as the particular elevation and degree of slope of the ground, i.e., plowing on the side of a hill, slippage of the tractor wheels, changes in soil structure and from other sources. To ensure that the tractor travels in the proper direction to produce the desired plowed furrows or results encompassing other production operations, such external forces must be overcome by effectively steering the tractor in a direction slightly deviating from the actual direction of travel.
Accordingly, it would be advantageous to provide a simple mechanical-electrical automatic tractor guidance system that could be easily installed on existing tractors of whatever kind to provide an accurate and sensitive electrical steering control to guide the tractor to follow previously plowed furrows. Additionally, it would be advantageous to provide an automatic tractor guidance system which adjusts for external forces tending to force the tractor to deviate from the desired direction of travel.